/Engine/Source/Runtime/NavigationSystem/Public/NavigationSystem.h
Looks up NavData appropriate for specified movement properties and returns it. NULL if not found; This is the encouraged way of querying for the appropriate NavData. It makes no difference for NavigationSystemV1 (AgentLocation and Extent parameters not being used) but NaV2 will take advantage of it and all engine-level AI navigation code is going to use call this flavor.
virtual [ANavigationData](API\Runtime\NavigationSystem\ANavigationData) * GetNavDataForProps ( const [FNavAgentProperties](API\Runtime\Engine\AI\Navigation\FNavAgentProperties) & AgentProperties, const FVector & AgentLocation, const FVector & Extent ) const